Touch controller and pen input system

ABSTRACT

A touch controller includes a processor and a memory coupled to the processor. The memory stores instructions that, when executed by the processor, cause the touch controller to: operate in an uplink power saving mode in which an uplink signal is transmitted with reduced power in response to reception of a suspend order from a host computer, and operate in a normal mode in which the uplink signal is transmitted with normal power in response to detection of a predetermined trigger during operation in the uplink power saving mode.

BACKGROUND Technical Field

The present disclosure relates to a touch controller and a pen inputsystem.

Background Art

There is a known pen input system including a pen and a pen inputapparatus that receives an input using the pen. The pen input apparatusis, for example, a tablet computer or a digitizer, and the pen inputapparatus generally includes a touch controller that detects the pen,and a host computer. The host computer is an apparatus that executesvarious types of software including an operating system, variousapplications, and drivers of various types of hardware. The driversexecuted by the host computer include a driver of the touch controller.

There are various known pens used in the pen input system. For example,International Publication Pamphlet No. WO. 2016/129194 (hereinafter,Patent Document 1) describes: a pen (first stylus 110) corresponding totwo-way communication between the pen and a pen input apparatus andconfigured to transmit a pen signal once the pen detects an uplinksignal transmitted by the pen input apparatus; a pen (second stylus 120)corresponding to only one-way communication from the pen to the peninput apparatus and configured to continuously transmit the pen signalwhile the power supply is on; and a pen (dual-mode stylus 130)corresponding to both of the two-way communication and the one-waycommunication, in which the pen alternately repeats the detection of theuplink signal and the transmission of the pen signal, shifts to thetwo-way communication when detecting the uplink signal, and shifts tothe one-way communication to repeatedly transmit the pen signal whendetecting a pen touch without detecting the uplink signal.

Furthermore, an operation called selective suspend is known in relationto a universal serial bus (USB) standard that is one of the standardsfor connecting a computer and a peripheral device (see “USB SelectiveSuspend”, [online], Jul. 7, 2011, Microsoft Japan Company, Limited,Windows & Devices Development Department, [Searched on Sep. 7, 2019],Internet <URL:https://blogs.msdn.microsoft.com/jpwin/2011/07/07/usb-2/>). This is anoperation for reducing the power consumption of the peripheral deviceconnected to the host computer through the USB, and the driver operatingon the host computer stops the transmission of start of frame (SOF) tolaunch the operation. Once the selective suspend is launched, theperipheral device operates with only minimum power necessary fordetecting a wake-up event and generating a restart signal when the eventoccurs. The wake-up event is, for example, small vibration in a case ofa mouse, and the peripheral device that has detected the wake-up eventreturns from the sleep state to the normal state.

However, the conventional selective suspend is not applied to the touchcontroller. This is because the pen that operates like the dual-modestylus of Patent Document 1 is rare, and the transmission of the uplinksignal transmitted by the touch controller cannot be stopped in thedetection of a typical pen corresponding to two-way communication andconfigured to transmit a signal after detecting the uplink signal. As aresult, the touch controller continues to always consume large power,and an improvement is necessary to reduce the power consumption.

SUMMARY

Therefore, an object of the present disclosure is to reduce the powerconsumption of a touch controller.

In addition, if the touch controller in the sleep state stopstransmitting the uplink signal, the pen corresponding to two-waycommunication cannot have an opportunity for transmitting the pen signaland cannot start to communicate with the touch controller.

Therefore, another object of the present disclosure is to enable tostart communication between a pen corresponding to two-way communicationand a touch controller even if the touch controller in the sleep statestops transmitting an uplink signal.

The present disclosure provides a touch controller a processor and amemory coupled to the processor, wherein the memory stores instructionsthat, when executed by the processor, cause the touch controller tooperate in an uplink power saving mode in which an uplink signal istransmitted with reduced power in response to reception of a suspendorder from a host computer, and operate in a normal mode in which theuplink signal is transmitted with normal power in response to detectionof a predetermined trigger during operation in the uplink power savingmode.

The present invention disclosure provides a pen input system including:an electronic pen which, in operation, transmits a pen signal; and atouch controller which operates in an uplink power saving mode in whichan uplink signal is transmitted with reduced power in response toreception of a suspend order from a host computer, and operates in anormal mode in which the uplink signal is transmitted with normal powerin response to detection of a predetermined trigger during operation inthe uplink power saving mode.

The present disclosure provides a pen input system including: anelectronic pen which, in operation, starts transmitting a pen signal inresponse to detection of a pen touch; and a touch controller whichoperates in an uplink power saving mode in which an uplink signal is nottransmitted in response to reception of a suspend order from a hostcomputer, and operates in a normal mode in which the uplink signal istransmitted in response to detection of the pen signal during operationin the uplink power saving mode.

According to the touch controller of the present disclosure, thepredetermined trigger can be used to return the touch controller to thenormal mode regardless of the uplink signal, and the power consumptionof the touch controller is reduced.

Furthermore, according to the pen input system of the presentdisclosure, the pen starts to transmit the pen signal in response to thedetection of the pen touch. Therefore, even when the transmission of theuplink signal is stopped in the uplink power saving mode, the touchcontroller can be triggered by the pen signal to return to the normalmode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram depicting a configuration of a pen input systemaccording to a first embodiment of the present disclosure;

FIG. 2 is a diagram depicting a sequence of signals transmitted andreceived between a touch controller and a pen;

FIG. 3 is a diagram depicting a process of the touch controlleraccording to a first example;

FIG. 4 is a diagram depicting a process of the touch controlleraccording to a second example;

FIG. 5 is a diagram depicting a process of the touch controlleraccording to a third example;

FIG. 6 is a diagram depicting a process of the touch controlleraccording to a fourth example; and

FIG. 7 is a diagram depicting a process of the touch controlleraccording to a fifth example.

DETAILED DESCRIPTION

An embodiment of the present disclosure will now be described in detailwith reference to the attached drawings.

FIG. 1 is a diagram depicting a configuration of a pen input system 10according to a first embodiment of the present disclosure. Asillustrated in FIG. 1 , a pen input system 10 includes a pen inputapparatus 1 and a pen 5.

The pen input apparatus 1 is an apparatus that realizes an input usingthe pen 5, and the pen input apparatus 1 includes a touch surface forthe pen input. Specifically, the pen input apparatus 1 is, for example,a tablet computer or a digitizer, and in the former case, the touchsurface includes a panel surface of a display.

The pen input apparatus 1 includes a sensor electrode group 2, a touchcontroller 3, and a host computer 4 as illustrated in FIG. 1 . Thesensor electrode group 2 includes a plurality of sensor electrodesarranged directly below the touch surface. The plurality of sensorelectrodes included in the sensor electrode group 2 include a pluralityof X electrodes 2 x extending in an illustrated y-direction and arrangedat equal intervals in an x-direction (direction orthogonal to they-direction) and a plurality of Y electrodes 2 y extending in theillustrated x-direction and arranged at equal intervals in they-direction.

The touch controller 3 is an integrated circuit connected to the sensorelectrode group 2. The touch controller 3 includes a processor 3 a thatis coupled to a memory 3 b storing instructions that, when executed bythe processor 3 a, cause the touch controller 3 to perform the variousacts described herein. The touch controller 3 can derive the position ofthe pen 5 in the touch surface and can also derive the position of afinger F in the touch surface. In a typical example, the touchcontroller 3 uses an active capacitive system to detect the pen 5 anduses a capacitance system to detect the finger F. The derivation of theposition of the pen 5 and the derivation of the position of the finger Fare alternately performed, which will be described in detail later. Thetouch controller 3 is configured to transmit a report indicating thederived position to the host computer 4 every time the touch controller3 derives the position of the pen 5 or the finger F. In addition to thederived position, the report also includes data (such as pen pressurevalue and pen identifier (ID)) transmitted by the pen 5 through a datasignal described later.

Here, the touch controller 3 and the pen 5 can use, for example, theactive capacitive system to perform two-way communication. Specifically,the touch controller 3 first uses the sensor electrode group 2 as atransmission antenna to periodically transmit an uplink signal US. Inresponse to reception of the uplink signal US, the pen 5 transmits a pensignal PS from an electrode (nib electrode) provided on a nib. The touchcontroller 3 receives the pen signal PS through capacitive couplingbetween the nib electrode of the pen 5 and the sensor electrode group 2and uses the result to derive the position of the pen 5.

The pen signal PS is a signal including: a burst signal that is anunmodulated carrier signal; and a modulated data signal with varioustypes of data. Of these, the burst signal is used by the touchcontroller 3 to derive the position of the pen 5. That is, the touchcontroller 3 detects the reception strength of the burst signal for eachof the plurality of sensor electrodes included in the sensor electrodegroup 2. The touch controller 3 then derives the position of the pen 5based on the position of each sensor electrode and the receptionstrength in each sensor electrode.

The data signal is a signal used to transmit various types of data fromthe pen 5 to the touch controller 3. The various types of datatransmitted through the data signal include a pen ID uniquely allocatedto each of a plurality of pens 5, a pen pressure value indicating thepressure applied to the nib of the pen 5, and the like. The pen ID isstored in advance in a memory of the pen 5. The pen pressure value isdetected by a pressure sensor built in the pen 5. The specific type ofdata transmitted by the pen 5 through the data signal is instructed fromthe touch controller 3 by using a command in the uplink signal US.

FIG. 2 is a diagram depicting a sequence of signals transmitted andreceived between the touch controller 3 and the pen 5. In FIG. 2 and thedrawings described later, a signal B represents a burst signal includedin the pen signal PS, and a signal D represents a data signal includedin the pen signal PS. A reception period Ra represents a receptionperiod of the burst signal B, and a reception period Rb represents areception period of the data signal D. A reception period Rp representsa reception period of the uplink signal US, and a period T represents adetection period of a touch operation using the finger F.

As can be understood from FIG. 2 , the touch controller 3 operating in anormal mode repeatedly transmits the uplink signal US at a certain cycleT1 (first cycle). The touch controller 3 also performs a receptionoperation of the burst signal B transmitted by the pen 5 just after thetransmission of the uplink signal US and detects a touch operation usingthe finger F in the first cycle T1. Note that the transmission voltageof the uplink signal US in this case is a first voltage (for example,9V).

Before receiving the uplink signal US, the pen 5 waits to receive theuplink signal US. Once the pen 5 approaches the touch surface so thatthe uplink signal US can be received, the pen 5 receives the uplinksignal US transmitted first after the approach. In the example of FIG. 2, the pen 5 enters the reception range of the uplink signal US at timet0. Hereinafter, the pen 5 entering the reception range of the uplinksignal US will be referred to as “pen-down.”

Once the pen 5 receiving the uplink signal US after the pen-downtransmits the burst signal B in response to the uplink signal US, thetouch controller 3 receives the burst signal B and derives the positionof the pen 5 as described above. The pen 5 also transmits the datasignal D, following the burst signal B. The touch controller 3 alsoreceives the data signal D and demodulates the data signal D to acquirethe data transmitted by the pen 5. Subsequently, although notillustrated in FIG. 2 , the touch controller 3 generates a reportincluding the derived position and the acquired data and outputs thereport to the host computer 4.

FIG. 2 also illustrates time t1 at which the nib of the pen 5 touchesthe touch surface. Hereinafter, the nib of the pen 5 touching the touchsurface will be referred to as “pen touch.” Although the pen pressurevalue detected by the pen 5 changes to a value greater than 0 after thepen touch, the configuration of the transmitted and received signals aresimilar to before the pen touch.

FIG. 1 will be described again. The host computer 4 is an apparatusincluding a processor, a memory, and various input-output apparatuses,such as a display and a communication apparatus. The touch controller 3is one of the various input-output apparatuses provided on the hostcomputer 4. The host computer 4 can execute various types of softwareincluding an operating system, various applications, and drivers ofvarious types of hardware. The drivers include a driver 4 a of the touchcontroller 3. The various applications include a drawing applicationthat draws a picture by generating stroke data based on a pen input.

Part of the functions of the drawing application regarding the pen inputwill be specifically described. Once the drawing application receives areport from the touch controller 3, the drawing application firstacquires position data in the report. The drawing application thengenerates stroke data including a series of control points based on aplurality of pieces of sequentially acquired position data. When thereport includes a pen ID, the drawing application also performs aprocess based on the pen ID. The process is, for example, a process ofsetting a drawing color in the stoke data when the drawing color is setin association with the pen ID in the application. The drawingapplication further performs a process of setting the line width, thetransparency, or the like of the stroke data according to a pen pressurevalue when the pen pressure value is included in the report.

The driver 4 a performs a process of receiving the report from the touchcontroller 3 and transferring the report to various applications andalso performs a process of transmitting a suspend order to the touchcontroller 3 when the reception of the report is ceased for a certaintime. Note that the transmission of the suspend order may be physicallyperformed by transmitting a predetermined signal from the driver 4 a tothe touch controller 3 or may be performed by stopping the transmissionof a signal (for example, the SOF) usually transmitted from the driver 4a to the touch controller 3. The touch controller 3 receiving thesuspend order enters into an uplink power saving mode in which the powerin transmitting the uplink signal is reduced. The touch controller 3then continuously performs a detection operation of a predeterminedtrigger and returns to the normal mode in response to detection of thepredetermined trigger as a result of the detection operation.

Five examples of a process performed by the touch controller 3 receivingthe suspend order will be described in detail.

FIG. 3 is a diagram depicting a process of the touch controller 3according to a first example. The touch controller 3 according to theexample decreases the transmission voltage of the uplink signal US toreduce the power in transmitting the uplink signal. In addition, the pensignal PS transmitted by the pen 5 in response to the uplink signal UStransmitted by decreasing the transmission voltage is used as thepredetermined trigger. The details will now be described.

The touch controller 3 enters into the uplink power saving mode afterreceiving the suspend order at time t2 and then transmits an uplinksignal US' instead of the uplink signal US. The uplink signal US' is asignal different from the uplink signal US in that the transmissionvoltage is a second voltage (for example, 3.3V) lower than the firstvoltage (for example, 9V). The operation of the touch controller 3 issimilar to the operation in the normal mode in other respects. Note thata “pen-down state” in the following description denotes a state in whichthe pen 5 is in the reception range of the uplink signal US transmittedin the normal mode.

The transmission voltage is low, and the reception range of the uplinksignal US' is narrower than the reception range of the uplink signal US.As a result, the pen 5 needs to be closer to the touch surface than inthe reception of the uplink signal US in order to receive the uplinksignal US′. In the example of FIG. 2 , although the pen 5 is in thepen-down state at time t3, the pen 5 cannot receive the uplink signalUS' transmitted just after time t3. This is because although the pen 5is in the reception range of the uplink signal US, the pen 5 is not inthe reception range of the uplink signal US' yet. However, when the useruses the pen 5 to perform the input, the pen 5 steadily approaches thetouch surface in a normal case. As a result, the pen 5 can receive thenext uplink signal US′. The touch controller 3 returns to the normalmode at time t4 in response to the reception of the pen signal PStransmitted by the pen 5 receiving the uplink signal US′.

FIG. 4 is a diagram depicting a process of the touch controller 3according to a second example. The touch controller 3 according to theexample extends the transmission cycle of the uplink signal US to reducethe power in transmitting the uplink signal. In addition, the pen signalPS transmitted by the pen 5 in response to the uplink signal US is usedas the predetermined trigger as in the first example. The details willnow be described.

The touch controller 3 enters into the uplink power saving mode afterreceiving the suspend order at time t5 and then changes the transmissioncycle of the uplink signal US from the first cycle T1 to a longer secondcycle T2 (>T1). Accordingly, the reception cycle of the burst signal Band the execution cycle of the touch detection operation are alsochanged from the first cycle T1 to the second cycle T2. The operation ofthe touch controller 3 is similar to the operation in the normal mode inother respects.

The transmission cycle of the uplink signal US is long, and thedetection timing of the pen 5 in the uplink power saving mode is laterthan in the normal mode. However, it is not that the pen 5 cannot bedetected forever, and the pen 5 can be eventually detected. In theexample of FIG. 4 , the touch controller 3 can detect the pen signal PStransmitted by the pen 5 at time t7 after the pen 5 enters into thepen-down state at time t6. Here, time t7 is time as much as second cycleT2 later than time t6. The touch controller 3 returns to the normal modein response to the detection of the pen signal PS.

FIG. 5 is a diagram depicting a process of the touch controller 3according to a third example. The touch controller 3 according to theexample reduces the transmission frequency of the uplink signal US toreduce the power in transmitting the uplink signal. In addition, the pensignal PS transmitted by the pen 5 in response to the uplink signal USis used as the predetermined trigger as in the first and secondexamples. The details will now be described.

The touch controller 3 enters into the uplink power saving mode afterreceiving the suspend order at time t8 and then changes the transmissionfrequency of the uplink signal US from a first frequency (once in firstcycle T1) to a second frequency (for example, once in n times the firstcycle T1, where n is an integer equal to or greater than 2). Note thatFIG. 5 illustrates an example of n=2. Accordingly, the executionfrequency of the reception operation of the burst signal B is alsochanged from the first frequency to the second frequency. The operationof the touch controller 3 is similar to the operation in the normal modein other respects.

The transmission frequency of the uplink signal US is low, and thedetection timing of the pen 5 in the uplink power saving mode is laterthan in the normal mode. However, it is not that the pen 5 cannot bedetected forever, and the pen 5 can be eventually detected. In theexample of FIG. 4 , the touch controller 3 can detect the pen signal PStransmitted by the pen 5 at time t10 after the pen 5 enters into thepen-down state at time 9. Here, time t10 is time as much as n×T1 laterthan time t9. The touch controller 3 returns to the normal mode inresponse to the detection of the pen signal PS.

FIG. 6 is a diagram depicting a process of the touch controller 3according to a fourth example. The touch controller 3 according to theexample stops the transmission of the uplink signal US to reduce thepower in transmitting the uplink signal. In addition, the detection ofthe finger touch is used as the predetermined trigger. The details willnow be described.

The touch controller 3 enters into the uplink power saving mode afterreceiving the suspend order at time t11 and then stops the transmissionof the uplink signal US. Accordingly, the reception operation of theburst signal B is also stopped. The operation of the touch controller 3is similar to the operation in the normal mode in other respects. In theexample, the touch controller 3 does not transmit the uplink signal US,and the pen 5 cannot transmit the pen signal PS. Although there ispen-down at time t12 in the example of FIG. 6 , the uplink signal US isnot transmitted, and the pen 5 does not transmit the pen signal PS.Therefore, the reception of the pen signal PS cannot be used as thetrigger to return the touch controller 3 to the normal mode.

Therefore, the touch detection operation periodically performed by thetouch controller 3 is used in the example. Specifically, the touchcontroller 3 is returned to the normal mode in response to the detectionof the touch operation of the finger F at time t13. In this way, thetransmission of the uplink signal US is restarted, and the touchcontroller 3 can detect the pen 5 as usual.

FIG. 7 is a diagram depicting a process of the touch controller 3according to a fifth example. In the example, the pen 5 is configured tostart the transmission of the pen signal PS in response to the detectionof the pen touch. Note that the pen 5 can detect the pen touch when thepressure sensor detects application of pressure to the nib (that is,when the pen pressure value becomes a value greater than 0). The touchcontroller 3 is configured to stop the transmission of the uplink signalUS to reduce the power in transmitting the uplink signal and configuredto intermittently perform the reception operation of the pen signal PS(burst signal B) while the touch controller 3 is in the uplink powersaving mode. The predetermined trigger in the example is the pen signalPS received in the reception operation. The details will now bedescribed.

The touch controller 3 enters into the uplink power saving mode afterreceiving the suspend order at time t14 and then stops the transmissionof the uplink signal US. The touch controller 3 also performs thereception operation of the burst signal B when the touch controller 3 isnot performing the touch detection operation. The operation of the touchcontroller 3 is similar to the operation in the normal mode in otherrespects.

Once the pen 5 detects the pen touch at time t15, the pen 5 transmitsthe burst signal B for a certain period. The pen 5 then returns to thereception waiting state of the uplink signal US. The touch controller 3returns to the normal mode at time t16 in response to the detection ofthe burst signal B transmitted in this way. The transmission of theuplink signal US is then restarted, and the touch controller 3 candetect the pen 5 as usual.

As described above, according to the present embodiment, thepredetermined trigger can be used to return the touch controller 3operating in the uplink power saving mode to the normal mode regardlessof the uplink signal US (that is, without transmitting the uplink signalUS during the operation in the uplink power saving mode). This canreduce the power consumption of the touch controller 3.

Particularly, the pen 5 starts to transmit the pen signal PS in responseto the detection of the pen touch according to the fifth example.Therefore, even when the transmission of the uplink signal US is stoppedin the uplink power saving mode, the touch controller 3 can be triggeredby the pen signal PS to return to the normal mode.

Although the preferred embodiment of the present disclosure has beendescribed, the present disclosure is not limited to the embodiment inany way, and it is obvious that the present disclosure can be carriedout in various modes without departing from the scope of the presentdisclosure.

For example, the first to fifth examples may be independently used ormay be used in any combination. For example, the touch controller 3entered into the uplink power saving mode may decrease the transmissionvoltage of the uplink signal US and extend the transmission cycle toreduce the transmission frequency. Furthermore, when the transmission ofthe uplink signal US is stopped to reduce the power in transmitting theuplink signal, both of the detection of the finger touch and thedetection of the pen signal PS in response to the detection of the pentouch by the pen 5 may be used as the predetermined triggers forreturning to the normal mode. Furthermore, the detection of the fingertouch may be used as the predetermined trigger for returning to thenormal mode even when the transmission of the uplink signal US is notstopped.

What is claimed is:
 1. A touch controller comprising: a processor; and amemory coupled to the processor, wherein the memory stores instructionsthat, when executed by the processor, cause the touch controller to:operate in an uplink power saving mode in which an uplink signal istransmitted with reduced power in response to reception of a suspendorder from a host computer; and operate in a normal mode in which theuplink signal is transmitted with normal power in response to adetection of a predetermined trigger during operation in the uplinkpower saving mode, wherein the uplink signal is transmitted at a firstvoltage while the touch controller operates in the normal mode; andwherein the uplink signal is transmitted at a second voltage lower thanthe first voltage while the touch controller operates in the uplinkpower saving mode.
 2. The touch controller according to claim 1,wherein: the detection of the predetermined trigger is a detection of apen signal transmitted by a pen.
 3. The touch controller according toclaim 1, wherein: the detection of the predetermined trigger is adetection of a touch operation by a finger.
 4. The touch controlleraccording to claim 1, wherein: the touch controller is configured toconnect to a sensor electrode group including a plurality of sensorelectrodes arranged below a touch surface, the touch controller, inoperation, derives a position of an object on the touch surface, andoutputs a signal indicating the position of the object on the touchsurface.
 5. The touch controller according to claim 4, wherein: thetouch controller, in operation, transmits the uplink signal using thesensor electrode group as a transmission antenna.
 6. The touchcontroller according to claim 4, wherein: the object is a pen thatoutputs a pen signal, and the touch controller, in operation, receivesthe pen signal through capacitive coupling between an electrode of thepen and the sensor electrode group, and derives the position of theobject based on the pen signal.
 7. The touch controller according toclaim 6, wherein: the detection of the predetermined trigger is adetection of the pen signal transmitted by the pen.
 8. The touchcontroller according to claim 6, wherein: the uplink signal indicatesthat a pen pressure value is to be transmitted by the pen to the touchcontroller.
 9. The touch controller according to claim 6, wherein: theuplink signal indicates that an identifier of the pen is to betransmitted by the pen to the touch controller.
 10. A method ofoperating a touch controller, the method comprising: operating the touchcontroller in an uplink power saving mode in which an uplink signal istransmitted with reduced power in response to receiving of a suspendorder from a host computer; and operating the touch controller in anormal mode in which the uplink signal is transmitted with normal powerin response to detecting a predetermined trigger during operation in theuplink power saving mode, wherein the operating the touch controller inthe normal mode includes transmitting the uplink signal at a firstvoltage during, and wherein the operating the touch controller in theuplink power saving mode includes transmitting the uplink signal at asecond voltage lower than the first voltage.
 11. The method according toclaim 10, wherein: the detecting the predetermined trigger includesdetecting a pen signal transmitted by a pen.
 12. The method according toclaim 10, wherein: the detecting the predetermined trigger includesdetecting a touch operation by a finger.
 13. The method according toclaim 10, wherein: the touch controller is configured to connect to asensor electrode group including a plurality of sensor electrodesarranged below a touch surface, and the method further comprises:deriving a position of an object on the touch surface, and outputting asignal indicating the position of the object on the touch surface. 14.The method according to claim 13, wherein: the object is a pen thatoutputs a pen signal, and the method further comprises: receiving thepen signal through capacitive coupling between an electrode of the penand the sensor electrode group, and the deriving the position of theobject includes the deriving the position of the object based on the pensignal.
 15. The method according to claim 14, wherein: the detecting thepredetermined trigger includes detecting a pen signal transmitted by thepen.
 16. A non-transitory processor-readable storage medium storinginstructions that, when executed by a processor, cause a touchcontroller to: operate in an uplink power saving mode in which an uplinksignal is transmitted with reduced power in response to reception of asuspend order from a host computer; and operate in a normal mode inwhich the uplink signal is transmitted with normal power in response toa detection of a predetermined trigger during operation in the uplinkpower saving mode, wherein the uplink signal is transmitted at a firstvoltage while the touch controller operates in the normal mode; andwherein the uplink signal is transmitted at a second voltage lower thanthe first voltage while the touch controller operates in the uplinkpower saving mode.
 17. The storage medium according to claim 16,wherein: the detection of the predetermined trigger is a detection of apen signal transmitted by a pen, or the detection of the predeterminedtrigger is a detection of a touch operation by a finger.
 18. The storagemedium according to claim 16, wherein: the touch controller isconfigured to connect to a sensor electrode group including a pluralityof sensor electrodes arranged below a touch surface, the touchcontroller, in operation, derives a position of an object on the touchsurface, and outputs a signal indicating the position of the object onthe touch surface.
 19. The storage medium according to claim 18,wherein: the object is a pen that outputs a pen signal, the pen signalis received through capacitive coupling between an electrode of the penand the sensor electrode group, and the instructions, when executed bythe processor, cause the touch controller to derive the position of theobject based on the pen signal.
 20. The storage medium according toclaim 19, wherein: the detection of the predetermined trigger is adetection of a pen signal transmitted by the pen.